Tablet-board.



No. 808,669. PATENTED JAN. 2, 1906. 0. B. MAGFARLANE.

TABLET BOARD.

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Mam 0 & fl/wiggw No. 808,669. PATENTED JAN. 2, 1906.

' O. B. MAGFARLANE.

TABLET BOARD.

APPLICATION FILED FEB. 28,1905.

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51 216066565: Jim/entan- 7% 0, WWW 64.404 fi/Y CHARLES B. MACFARLA NE, OF VVALTHAM, MASSACHUSETTS.

TABLET-BOARD.

Specification of Letters Patent.

Patented Jan. 2, 1906.

Application filed February 28, 1905. Serial No. 247,790.

To all whom it may concern.-

Be it known that I, CHARLES B. MAOFARLANE, of Waltham, in the county of Middlesex and State of Massachusetts, have invented an Innproved Tablet-Board, of which the following is a specification, reference being had to the accompanying drawings, making a part hereof, in which- Figure 1 is a top plan, and Fig. 2 a bottom plan, of the preferred form of my improved tablet-board. Fig. 3 is a section on lines 3 3 of Fig. 1.

The device known as a tablet-board or a panel-board consists, essentially, of a tablet of slate or like non-conductor fitted with conductors electrically connected to fuses, the larger conductors serving to connect groups of these fuses, so that the current can be distributed through any fuse to the smaller conductor connecting that fuse directly with the translating-circuit. These devices are in common use and have long been made in several styles, one style being adapted for several circuits of two wires each, and another style adapted for several circuits of three wires each, and a third style capable of being converted by changing the larger conductors from those of one style to those of the other.

My invention has for' its object to produce a device of this sort which can be used as a two-wire tablet-board and also as a threewire tablet-board without change and which is, in fact, a two or three-wire tablet-board.

I construct my improved tablet-board with two bus-bars a a, as the conductors for the larger currents are commonly called, on one face of the tablet A, with a bus-bar Z) between them, which is of opposite polarity in the case of a two-wire system and which is neutral in the case of a three-wire system.

I construct my improved tablet-board with two bus-bars a a on the front of thetabletAand with two bus-bars 0 c on the back of the tablet. The two bars 0 0 are connected by a bar 6', and this bar 6 is connected with a bar 6 on the front of tablet A, between bars a a. On the front of tablet A are also fixed fuse appliances B B, herein shown as sockets for fuseplugs. There are two sets of these sockets, of which one set is connected with the bars a and a and the other set with the bars 0 0', so that this form of my invention is adapted for four circuits, each of which may be either a two or athree wire circuit. Of course the board may be adapted to any number of circuits desired by building it with the proper number of fuse appliances.

The feeder-wires, which lead from the dynamo or other source of electrical pressure, are connected in the three-wire system one to bus-bar a, another to bus-bar a, and the third or neutral wire to the bus-bar b and through that with the bus-bars 0 and c, for in my improved tablet-board, when used for three-wire circuits, the cross-section of bus-bar 6 must be at least equal to the sum of the cross-sections of bus-bars cand 0'. One essential feature of my invention resides in a three-wire neutral conductor 6, 0, and c, the part?) of which is readily accessible from the face of the tablet A and the parts a c of which are cross-connected by the part b, as shown.

Another essential feature of my invention is that the bus-bars a a and c 0 are substantially parallel, c and 0 being embedded in recesses in the lower face of the board, the recesses being filled outside the bus-bars with insulating material and electrically connected by cross connections between bus-bars 0 and. 0 with bus-barb, and thereby avoid all cross connections on the upper face of the board, which are highly objectionable, as they lead to accidents from short-circuiting and grounds.

The sockets B and B are the usual fuse-plug sockets and are adapted to contain safetyplugs (not shown) with double poles. These safety-plugs are familiar to all skilled in the art and may be substituted by any other type of fuse.

What I claim as my invention is- A tablet-board of the character described comprising a tablet; three terminals fixed to the tablet; a pair of bus-bars fixed to the top face of the tablet and connected with two of the terminals, each bar being branched and each branch adapted to be connected with a fuse; a bus-bar on the opposite side of the tablet and connected with the other terminal, said bar being branched and each branch adapted to be connected with a fuse, all of the bars and terminals being separated and insulated so as to adapt the board for use under different conditions of voltage.

CHARLES B. MACFARLANE.

lVitnesses:

H. C. BowsER, G. A. ROCKWELL. 

